Ab initio phonon dispersions of single-wall carbon nanotubes -: art. no. 235409
Ab initio phonon dispersions of single-wall carbon nanotubes -: art. no. 235409
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DOI：
10.1103/physrevb.69.235409
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发表时间：
2004-06-01
影响因子：
3.7
通讯作者：
Han, R
中科院分区：
文献类型：
--
作者：
Ye, LH;Liu, BG;Han, R
用从头算超原胞方法计算了一系列单壁碳纳米管的声子色散曲线。在密度泛函理论和局域密度近似的框架下，采用模守恒赝势平面波方法计算了力常数。用累积力常数法代替原子间力常数法来构造动力学矩阵。我们得到了更好的低频色散比现有的结果，没有软声子模式。在整个频率范围内显示出良好的精度。松弛的单壁碳纳米管结构中的残余力通过线性拟合力常数方案过滤掉。用D-2群对称性重新分析了拉曼和红外激活模。发现频率与实验观察非常一致。我们的结果证实了A（1g）模式的频率下降。声子色散很好地解释了低温比热实验和中子散射实验中的一些问题。用同样的方法计算了石墨的声子色散，结果与实验符合得很好。从理论上分析了累积力常数法在获得较好的低频色散方面的优越性。
Phonon-dispersion curves for a series of single-wall carbon nanotubes (SWCNT's) have been obtained by ab initio supercell approach. Force constants are calculated using norm-conserving pseudopotential plane-wave method in the framework of the density-functional theory and local-density approximation. Cumulant force-constant method is used instead of interatomic force-constant method to construct the dynamical matrices. We get much better low-frequency dispersions than existing results with no soft phonon mode presented. Good accuracy is shown in the full frequency range. Residue forces in the relaxed SWCNT structures are filtered out by a linear fitting force-constant scheme. Raman and IR active modes are reanalyzed by D-2nd group symmetry. The frequencies are found to agree excellently with the experimental observations. Our results confirm the reported frequency drop of the A(1g) mode. Some issues in the low-temperature specific-heat experiment and the neutron-scattering experiment are well explained by our phonon dispersions. Phonon dispersions of graphite are also calculated using the same method, being in good agreement with experiment. Theoretical analysis is also presented to explain the advantages of cumulant force-constant method to get better low-frequency dispersions.